The present invention relates to colored solder materials and a method of forming a colored membrane on soldered portions by employing said materials. More particularly the invention relates to colored solder materials and a method of forming a colored membrane on the surface of soldered portions by employing said materials to facilitate visual inspection of the soldered portions in the production of electronic machinery, equipment and apparatus.
Hitherto, only solder with natural metallic coloration and sheen have been known. In surface mounting of electronic components on printed wiring boards, reflow soldering is carried out by employing solder cream or paste. After solidification of the solder, it is necessary to inspect the appearance of the solder configuration or fillet, etc. The above inspection has hitherto been carried out either by visual inspection or by employing an automatic optical inspection apparatus.
However, there are many difficulties in effectively carrying out such visual inspections, such as metallic glare and difficulty in discerning between the component leads and the solder. Furthermore, the automatic optical inspection apparatus sometimes indicated wrong inspection results due to halation, etc., ascribable to the metallic glare of the soldered portions.